(a) Field of the Invention
The present invention relates to a self-generating resistance apparatus for fitness and rehabilitation equipments, and more particularly to an apparatus that installs a power generator at a flywheel externally to increase the rotating speed ratio to produce a large power, and supply an electric current to a solenoid to produce a reverse resistance to the rotating flywheel, so as to achieve the exercise effect.
(b) Description of the Related Art
At early stage, American fitness equipments directly used an automobile power generator as a resistance system, but such application was unable to comply with the special requirements of the fitness equipments, and thus improvements were made as follows.
The first model is a resistance system in form of a pure power generator as shown in FIGS. 1A and 1B, wherein an inertia flywheel 12 and an iron core 14 are installed on a shaft 11, and a power generating coil 15 is wound around the circumference of the iron core 14, such that when the inertia flywheel 12 and a permanent magnet 13 installed at the internal periphery of the inertia flywheel 12 are rotated, a power generator 10 is formed. Related technologies of this sort are disclosed in U.S. Pat. Nos. 4,775,145, 5,558,624, and 5,236,069, but these prior arts have the following drawbacks:
1. Since the source of resistance is produced by connecting the power of the power generator in a reverse direction, and the original power generator is short-circuited to produce a braking effect whenever a resistance is required. A greater braking force and a greater rotating speed ratio are required for the design, thus incurring a higher level of difficulty for the manufacture.
2. A multiple of harmonic waves of the reversely connected power supply as described in the first drawback produce significant vibrations and noises at a high rotating speed.
3. A portion of the power generated by the power generator is consumed, so that it is necessary to install a large resistor to consume the remaining portion of the power, thus incurring a higher cost and a lower efficiency.
The second model is a mixed-type power generator that adds a solenoid 16 and an iron core 17 onto an external side of the inertia flywheel as shown in FIGS. 2A and 2B. The structure of this sort is disclosed in U.S. Pat. No. 6,084,325, and the remaining portion of the power of the pure power generator is used for producing a braking force to achieve the required resistance for the fitness equipments and rehabilitation equipments. Although this mixed-type power generator can overcome the high cost and low efficiency of the pure power generator, yet it has the following drawbacks:
1. The mixed-type power generator comes with a fixed structure. Since a constant air gap is kept between the solenoid 16 and the iron core 17 and the inertia flywheel 12 for high performance, therefore the size of the power generator cannot be varied freely according to user requirements.
2. Since the iron core 14 of the power generator and the iron core 17 of the solenoid 16 are two separate systems, therefore the price will be higher.
3. The solenoid 16 is an independent component installed outside the inertia flywheel 12, so that the volume will be larger, which is unfavorable for the overall design of an automobile
The third model is also a mixed-type power generator, wherein a solenoid 16 and an iron core 17 are installed on the internal side of the inertia flywheel as shown in FIGS. 3A and 3B. The structure of this sort is disclosed in U.S. Pat. No. 7,732,961. Although this model can overcome most of the drawbacks of the second model, yet the power generator adopts a large pulley to drive a small pulley of the fitness equipments or rehabilitation equipments by a one-step transmission method, so that the rotating speed ratio is generally less than 1:20 which is relatively low. Since the efficiency of the power generator is related to the rotating speed of the power generator closely, therefore if the power generator has a high rotating speed, then it will output a high power; and if the power generator has a low rotating speed, then it will output a low power. Obviously, the rotating speed of the aforementioned three models of power generators is limited, thus failing to maximize the efficiency of their applications.